Drug Chemistry
L-hyoscyamine is one of three important alkaloids in belladonna, stramonium and hyoscyamus extracts. The other two are atropine and hyoscine(scopolamine). Many years after the isolation of L-hyoscyamine and atropine from solanaceous plant extracts, it was discovered that atropine is a racemic mixture of two enantiomers, L-hyoscyamine and D-hyoscyamine. Hence, one-half of atropine is L-hyoscyamine.
The original alkaloid formed in the plant is L-hyoscyamine. At the time of harvest little, if any, atropine is present in the plant. However, there is a tendency for the enantiomer to racemize. Hence during the process of extraction and concentration of the L-hyoscyamine, some of the alkaloid is converted to D-hyoscyamine resulting in the racemic mixture called atropine (D,L-hyoscyamine).
Enantiomers are identical in molecular weight and have identical physical and chemical properties except for their effect upon a plane of polarized light. However, in physiological action, they may be distinctly different. The physiological effects of the racemic mixture is of course equivalent to the sum total of the individual enantiomeric effects.